However, the word "Mushroom World" is also the conjectural name used by Mario fans to describe the planet composed of most of the lands, kingdoms, and islands seen and mentioned throughout the Mario series, including the Mushroom Kingdom and all the lands depicted in Super Mario Bros. 3. This Mushroom World should not be confused with the Mushroom Kingdom which is just one kingdom in a greater world. Additionally, the Mushroom World should not be confused with the Marioverse. The Mushroom World is a specific place while the Marioverse encompasses everything related to Mario. For example, the land of Subcon is not part of the Mushroom World, as it is a world that exists in dreams. However, Subcon is part of the Marioverse.

Additionally, the Mushroom World is orbited by two moons, both smaller than Earth's moon. The larger can be traversed in several "screens," and the smaller can be covered in a few seconds. Mario has visited both. In Paper Mario: The Thousand-Year Door, Mario was shot to the large moon to reach the X-Naut Fortress and the last Crystal Star. In Yoshi's Island, Yoshi and Baby Mario were kicked to the small moon, where they had to fight Raphael the Raven. The smaller one is extremely dense for its size, having gravity similar to the planet's. In addition, both apparently have atmospheres similar to the Mushroom World's.

Also, as depicted in Super Mario Galaxy, the planet is orbited by several hundred space rocks, and mini-planets. All of these are inhabitable, as Mario can survive, and you find many enemies on these that can also survive. Even plant life grows on some of them. Lumas also live in the outer space of Mushroom World, with their "Mother", Rosalina.